With a certain type of thin client system, technology to remotely control updating of a screen of a computer is employed. For example, familiar protocols to be used for remote control of a screen include RDP (Remote Desktop Protocol) and RFB (Remote Frame Buffer) protocol.
For example, with a certain type of thin client system, the server generates data for having a thin client render a screen, and transmits the generated data to the thin client. The server repeats generation and transmission of data as described above, thereby remotely controlling updating of a screen of the thin client.
Recently, thin client systems have attracted attention from some perspectives such as a perspective to suppress leakage of information from a computer, a perspective to reduce maintenance cost of a computer, and so forth. Usage for thin client systems is spreading, and variously studies regarding thin client systems are being performed.
For example, the following technology has been proposed with is as an issue to improve operation response while maintaining versatility of a thin client.
An information processing device according to this technology includes image memory, a change frequency discriminating unit, a first image transmission unit, a high-frequency change area identifying unit, a transmission stopping unit, and a second image transmission unit. The image memory holds an image to render an execution result of a computer. The change frequency discriminating unit divides an image rendered in the image memory into multiple areas, and discriminates frequency in change between frames for each area.
The first image transmission unit transmits an image of a changed area. The high-frequency change area identifying unit identifies an area of which the frequency in change exceeds a threshold as a high-frequency change area. The transmission stopping unit stops transmission at the first image transmission unit regarding an identified area. The second image transmission unit subjects the image of an identified area to moving image compression processing of which the compression rate is higher than that of the first image transmission unit and transmits this.
Incidentally, remote control of updating of a screen accompanies network communication. For example, with a certain type of thin client system, the server transmits data for remotely controlling updating of a screen a thin client to the thin client via a network. Length of time since the server transmitted data until the thin client receives the data depends on network conditions. Accordingly, fairly long display delay may occur depending on network conditions.
On the other hand, technology for recognizing network conditions is also variously studied. For example, network conditions may be represented with the available bandwidth of a network or may be represented with route cost on a network. With regard to available bandwidth or route cost, the following technology has been proposed, for example.
A certain method is a method for measuring the available bandwidth of a network with high speed and high precision. According to this method, multiple cyclic timestamp packets are transmitted to a communication device on the reception side with an examination transmission rate that has currently been set. Based on time when each of the timestamp packets is received at the communication device on the reception side, change tendency of transmission delay time difference between timestamp packets is inspected.
In the event that the transmission delay time difference is not included in a predetermined stable range, and also exhibits an increasing trend, inspections are repeated after decreasing the value of the examination transmission rate. On the other hand, in the event that transmission delay time difference is not included in the stable range, and also exhibits a declining trend, inspections are repeated after increasing the value of the examination transmission rate. As results of processing as described above, in the event that the transmission delay time difference is included in the stable range, the examination transmission rate that has currently been set is determined as available bandwidth.
Also, the following system has also been proposed relating to route cost. This system is a system to select the optimal route in the event that there are multiple routes to reach the same node. Specifically, this system is a system to select the optimal route in a multi-node network including a first route from the start-point node to the end-point node via a first node, and a second route from the start-point node to the end-point node via a second node. This system includes a storage unit and a route measurement optimizing unit.
The storage unit stores link cost. Also, the route measurement optimizing unit compares first roust cost and second route cost to select a route with lower cost, thereby optimizing the route. Note that the first route cost is specifically, calculated based on start-point node cost, first link cost, first node cost, second link cost, and end-point node cost. Also, the second route cost is calculated based on start-point node cost, third link cost, second node cost, fourth link cost, and end-point node cost.
With a certain type of system, an image to be displayed on the screen of a first computer is generated by a second computer. In this case, the second computer transmits screen information to cause the first computer to display the image on the screen, to the first computer. Next, the first computer receives the screen information, and displays the image on the screen in accordance with the screen information. Generation of an image, transmission of screen information, and display of an image as described above may repeatedly be performed.
Specifically, generation of an image at the second computer is based on input given to the first computer via an input device of the first computer. The first computer transmits notification regarding input to the second computer, and the second computer executes, in response to notified input, one or more programs. The second computer generates, in response to executions of one or more programs, an image as described above.
In the event that the first and second computers have operated as described above, this is recognized by a user for the first computer as follows. Specifically, this is recognized by the user such that, in response to input given to the first computer by the user via the input device, the screen of the first computer is updated.
In this case, length of time since the user gave input to the first computer via the input device until the first computer displays an image on the screen in response to screen information affects on usability. The length of this time depends on network conditions between the first and second computers. Therefore, it is desirable that some sort of control according to the network condition be performed in order to suppress deterioration in usability even if the network condition is poor.
On the other hand, in order to control according to the network condition, if additional communication to recognize the network condition is excessively performed, the network condition may become worse. This is because load for the network is further increased due to additional communication. Deterioration in the network condition results in deterioration in usability. Accordingly, it is desirable that the amount of additional communication is not great as a point of view for usability in the system including the first and second computers as described above.
Japanese Laid-open Patent Publication Nos. 2011-238014, 2006-74773, and 2006-237837 are examples of the related art of the present technology.